The present invention relates to a machining assembly including a cutting tool for machining wood, plastics or the like which is connected to an exhaust hood to permit optimum chip removal. More particularly, the present invention relates to a machining assembly as put to use for machining board or panel-type workpieces in a fixed arrangement or on the fly. If the chips fail to be exhausted optimally from such tools the machined surface can be marred by the remaining chips, which is undesirable.
Conventionally, chips resulting from machining wood, plastics or the like such as, for example, wood-replacement or composite materials are exhausted via an exhaust device in the vicinity of the action site between cutter and workpiece. Experience has shown such an exhaust to be inadequate, however, resulting in chips partly being cat multiply which reduces the useful life of the cutting tools, or leaves the machined workpiece surface marred. Known furthermore are the problems involved with cemented materials, often resulting in a conglomerate of cement and chips which may lead to clumping greatly obstructing chip removal as a whole.
From the concluding report on the development of molding tools incorporating internal chip removal by the Institute of Wood and Paper Engineering of the Technical University of Dresden, delivered Apr. 27, 1999 a molding tool is known comprising a chip receiving opening sited directly before the cutter. The chip receiving opening is connected to a cavity in the interior of the tool, the cavity in turn features an axial ejection opening for chip removal which is open to the side facing away from the drive spindle. In the tool cavity of the molding tool a cylindrical or conical insert is provided fixed in the frame and which is adapted thin-walled to the internal shape of the tool, whereby at least one window is provided in the active site of the tubular insert. In addition, located at the inner side of the tubular insert downstream of the chip window is a slanting guide element extending over the fall width of the tubular insert. In this way, chips can be exhausted from the active site trough the tool to the side facing away from the spindle driving the tool. The tool itself in this arrangement is penetrated only in the radial direction.
Known furthermore are machining assemblies whose tools comprise several aims provided with cutters with which the workpieces can be machined. Exhausting the resulting chips in this arrangement is done via an exhaust hood arranged at the drive spindle side of the tool. The exhaust hood features a substantially U-shaped configuration so that the exhaust hood is totally open in one direction. Exhausting air and chips from the exhaust hood in this arrangement is done at the side opposite the opening of the exhaust hood.
The present invention is based on the technical problem of providing a machining assembly including a cutting tool effectively permitting optimum chip removal with minimum complication in fabrication and low operating costs whilst preventing chip clumping.
This objective is achieved by a machining assembly having the features as set forth in claim 1.
The gist of the present invention is to exploit the natural direction of chip motion materializing at the cutter of a cutting tool for its removal. For this purpose a portion of a disk-shaped section of the cutting tool adjoining the cutter thereof is now penetrated for the first time both axially and totally radially by a chip receiving opening.
At the same time, a fixed exhaust hood arranged coaxial to the rotating tool and at its machine spindle side is provided with a likewise fixed ring extending almost filly up to the cutters of the tool so that only a minor gap remains between the cutters and the ring on the exhaust hood. The exhaust hood with the ring arranged thereon totally encircles the tool circumferentially and at least in part axially in thus effectively preventing accumulation or clumping of chips or conglomerations of chips and cement. The chips materializing at the cutter are directed axial into a quill of the tool through the chip receiving opening in practically preventing them from coming into contact with the rotating tool. In this arrangement, the direction of chip motion materializing at the cutter is supported by the air being exhausted from the exhaust hood. Due to the air being swirled in the region of the chip receiving opening as well as the air being exhausted from the exhaust hood the chips are prevented from becoming deposited at the ring of the exhaust hood directly adjoining the cutters. Should deposits of chips or a conglomerate of chips and cement nevertheless occur at this ring, these are always mechanically removed by the tool itself with the edge defining the chip receiving opening, in thus considerably improving chip removal whilst effectively preventing clumping or blockage by a conglomerate of chips and cement.
It is in this way that the chips materializing at the cutter of the tool can be removed particularly effectively from the cutting tool since the natural direction of chip motion is supported by the exhaust air flow. At the same time, the volume of air to be exhausted can be maintained small since the chips do not need to be deflected by the air flow. Removing the chips axially through the tool offers the additional advantage that the geometry of the side of the tool facing the workpiece can now be freely configured without needing to taking into account chip exhaust in this area. This also prevents chips from coming into contact with the workpiece to be machined or the already machined surface thereof. Such machining assemblies in accordance with the invention are particularly suitable for machines working on the fly.
In accordance with one preferred embodiment of the present invention the exhaust hood can be adapted variable to the diameter of the disk-shaped section of the cutting tool so that the width of the gap between the disk-shaped section of the cutting tool and the inner edge of the exhaust hood remains a minimum. This is achievable, for example, via an annular insert adapted to the inner diameter of the exhaust hood at the outer diameter of the disk-shaped section of the tool. By minimizing the gap between the cutting tool and the exhaust hood an unnecessarily high exhaust capacity of the exhaust hood is avoided in thus achieving reduced operating costs.
Preferably, the exhaust opening in the cowled exhaust hood, via which air and chips are removed from the cowled exhaust hood, is arranged staggered by 20xc2x0 to 150xc2x0 in the direction of motion of the tool cutter relative to the chip production site, an arrangement being particularly preferred in which the exhaust hood is arranged staggered by 90xc2x0 in the direction of motion of the tool cutter relative to the chip production site. This permits assuring that, in addition to the natural motion of the chip in the axial direction, the motion of the chip in the radial direction generated by the centrifugal forces is made use of for chip removal. The air exhaust through the opening in the cowled exhaust hood is thus able to optimally support and boost the natural direction of motion of the chip in thus permitting effective chip removal.